Metodos rapidos de estimacion de nitrogeno potencial-mente mineralizable en suelos

Abstract

The objective of this study was to relate potentially mineralizable soil nitrogen (N) obtained by means of long-term aerobic incubations (No), with nitrogen mineralizated using more rapid and simple methods such as KCl digestion (Nq) and short-term anaerobic incubations at 40 °C (Na). A preliminar experience, carried out on 23 soil samples of the southeastern Buenos Aires Province, allowed to determine that a close association between nitrogen mineralization after 7 and 14 days of anaerobic incubations (Na) exists. Consequently, Na was incubated during 7 days. Measurements were made during 1994 to 1997 in the topsoil of soils submitted to contrasting management systems of the Pampean Region. Nq had the lowest range in samples taken in 1994 and 1995. This indicated its low sensitivity, showing no differences between managements. In both years the relationships between No and Nq were similar; however slopes were different suggesting that Nq was not a good predictor of No. Short-term anaerobic incubations at 40 °C and No were correlated in both years, and the slopes of the fitting equations obtained in each year were not different (P<0,05). This relationship was confirmed with soil samples taken during 1996 and 1997. The fitting equation for the four analysed years was No = 1,37 Na + 83,17 (r2 = 0.65), which can be used to estimate No with a rapid incubation method (Na).